A D/A converter for converting discrete digital data into continuous analog signals can be a converter of ladder resistance network type, segment type, integral type, etc. A converter of ladder resistance network type is configured by combining a ladder-shaped resistance network with a plurality of analog switches, and retrieves analog output from the end of the resistance network by controlling the analog switch using a digital input value.
A converter of segment type is configured by 2n-1 constant current circuits, and obtains analog output by adding a current with the switch corresponding to the digital input value turned on. A converter of integral type integrates a constant current using a mirror integration circuit while counting a clock value specified by a digital input value using a counter, and the resultant integral value is obtained as analog output.
Normally, in analog signal processing, the concept of the analog technology such as the reflection and a delay of a signal, the consistency of a transmission line, etc. is to be applied to circuit design, and the circuit design cannot be performed ad in digital data processing. Therefore, to perform the analog signal processing, a circuit applicable to the analog technology is to be designed, and to perform the digital data processing, a circuit applicable to the digital technology is to be designed.
However, any type of the above-mentioned conventional D/A converter is configured by a digital portion and an analog portion in a random mixed manner in the entire process of inputting digital data and outputting an analog signal. Therefore, there has been the problem that it is very difficult to design a circuit appropriate for the analog signal processing and the digital data processing.
The present invention has been achieved to solve the above problem. It is an object of the present invention to completely separate the digital portion and analog portion thereby facilitating the designing of circuits suitable for the portions.